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Abstract:

A method of low temperature sterilization that with the use of a compact
simple apparatus, is capable of safe, unfailing sterilization. There is
provided an apparatus comprising gas cylinder (gas supply source)(8),
high energy particle generation part (1-3) capable of generating a gas of
temperature nonequilibrium condition containing high energy particles
through exciting of the gas supplied from the gas cylinder (8) and gas
blow part (4) capable of jetting the gas of temperature nonequilibrium
condition generated by the high energy particle generation part (1-3)
over pathogenic microbes positioned outside.

3: The low-temperature dry disinfection device according to claim 2,
wherein the high-energy particle generator further comprises:a chamber
for receiving the gas supplied from the gas supply source;an
electromagnetic field generation unit for providing the chamber with an
electromagnetic field for exciting the gas in the chamber; anda
high-voltage power supply for supplying the electromagnetic field
generation unit with power voltage, the gas spraying unit further
comprising a gas spraying pipe connected to the chamber.

4: The low-temperature dry disinfection device according to claim 2,
wherein the high-energy particle generator further comprises a cooling
apparatus for cooling down the gas of temperature nonequilibrium
condition before the gas is introduced into the gas spraying unit.

5: The low-temperature dry disinfection device according to claim 2,
wherein the gas supply source supplies a single type of gas or a mixed
gas of more than two types of gases.

6: The low-temperature dry disinfection device according to claim 2,
wherein the high-energy particle generator further comprises a flow rate
regulating valve arranged at a gas supply port for receiving gas from the
gas supply source.

7: The low-temperature dry disinfection device according to claim 2,
wherein at least one of the high-energy particle generator and the gas
spraying unit is provided with means for mixing steam into the gas of
temperature nonequilibrium condition.

Description:

TECHNICAL FIELD

[0001]The present invention relates to a technique for killing bacteria
living on the surface of objects or living organisms by use of high
energy particles or the like in the air.

TECHNICAL BACKGROUND

[0002]Recently, infectious diseases caused by bacteria such as severe
acute respiratory syndrome (SARS) or avian flu suddenly and globally
occur and cause a serious social problem. People are highly aware of this
problem and ask for a safe and easy-to-handle sterilization and
disinfection method.

[0003]Meanwhile, in a medical institution or a general household,
sterilization and disinfection is generally carried out by use of
antiseptic solution. However, there is no perfect antiseptic solution
which combines safety and effectiveness and effective and therefore,
different types of antiseptic solutions are only used in accordance with
intended use. Sterilization and disinfection in a breeding area of farm
animals for food currently relies on dispersion of disinfectant and is
not sufficient. Therefore, development of prevention transmission
technique for the farm animals is also a pressing problem.

[0004]Furthermore, a disinfection device using ethylene oxide gas, a
disinfection device using a hydrogen peroxide low-temperature gas plasma
and a disinfection device using radiation or the like are known as
conventional compact low-temperature disinfection devices for medical
use. However, the disinfection device using ethylene oxide gas has a
disadvantage of using carcinogenic material which is legal restrained.
The disinfection device using hydrogen peroxide low-temperature gas
plasma requires a vacuum device, is high in cost, and operation of the
apparatus is not easy. The disinfection device using radiation requires
an expensive radiation generator and the limited installation location.
Moreover, each of the disinfection devices are intended to sterilize
medical equipments and batch sterilization method is adopted. Therefore,
an object of sterilization is limited. [0005][Patent Document 1 ]
Japanese Laid-Open Patent Publication No. H6-23023 [0006][Patent Document
2] Japanese Laid-Open Patent Publication No 2002-85531

DISCLOSURE OF THE INVENTION

Problem to be Solved by the Invention

[0007]It is an object of the present invention to provide a
low-temperature sterilization method achieving safe and reliable
sterilization by use of a compact and simple apparatus.

Means for Solving the Problem

[0008]To solve the above-mentioned problem, according to the present
invention, there is provided a dry sterilization method comprising the
steps of: generating gas of temperature nonequilibrium condition
containing high-energy particles by exciting gas; and spraying pathogenic
microorganisms with the gas of temperature nonequilibrium condition so as
to kill the pathogenic microorganisms.

[0009]Here, "the gas of temperature nonequilibrium condition" means, for
example, gas which contains particles having internal energy high enough
to kill pathogenic microorganisms while, on the other hand, has small
thermal energy and an energy condition suitable for accomplish the end
desired.

[0010]To solve the above-mentioned problem, according to the present
invention, there is provided a low-temperature dry disinfection device
comprising: a gas supply source; a high-energy particle generator for
generating gas of temperature nonequilibrium condition containing
high-energy particles by exciting the gas supplied from the gas supply
source; and a gas spraying unit for spraying external pathogenic
microorganisms with the gas of temperature nonequilibrium condition
generated by the high-energy particle generator.

[0011]In the above-mentioned configuration, it is preferable that the
high-energy particle generator further comprises: a chamber for receiving
gas supplied from the gas supply source; an electromagnetic field
generation unit for providing the chamber with an electromagnetic field
for exciting the gas in the chamber; and a high-voltage power supply for
supplying power voltage to the electromagnetic field generation unit, the
gas spraying unit further comprising a gas spraying pipe connected to the
chamber.

[0012]Furthermore, it is preferable that the high-energy particle
generator further comprises a cooling apparatus for cooling down the gas
of temperature nonequilibrium condition before the gas is introduced into
the gas spraying unit. It is also preferable that the gas supply source
supplies a single type of gas or a mixed gas of more than two types of
gases.

[0013]Furthermore, it is preferable that the high-energy particle
generator further comprises a flow rate regulating valve arranged at a
gas supply port for receiving gas from the gas supply source. It is also
preferable that at least one of the high-energy particle generator and
the gas spraying unit is provided with means for mixing steam into the
gas of temperature nonequilibrium condition.

Effect Of The Invention

[0014]According to the present invention, sterilization is carried out by
spraying an object or living organisms with gas of temperature
nonequilibrium condition including high energy particles, thereby
sterilization effect enough to kill bacteria can be obtained, while
damage to the object or the living creature can be significantly reduced.
In addition, when metals or other heat resistant materials are selected
as an object to be sterilized, by injecting the gas at the temperature of
more than 50° C., it is possible to cut down the time for
sterilization.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015][FIG. 1] A view showing a schematic configuration of a low
temperature dry disinfection device according to one embodiment of the
present invention.

[0016][FIG. 2] A photograph of spores of Bacillus subtilis coated on a
surface of a sample which is not sterilized.

[0017][FIG. 3] A photograph of spores of Bacillus subtilis coated on a
surface of a sample which is sterilized by argon plasma radiation (353K).

[0018][FIG. 4] A photograph of spores of Bacillus subtilis coated on a
surface of a sample which is sterilized by heated argon gas (353K).

[0019][FIG. 5] A photograph of spores of Bacillus subtilis coated on a
surface of a sample which is sterilized by UV radiation.

[0029]Hereafter, a preferred embodiment of the present invention will be
explained with reference to attached drawings. FIG. 1 is a view showing a
schematic configuration of a low temperature dry disinfection device
according to one embodiment of the present invention.

[0030]According to FIG. 1, the low temperature dry disinfection device of
the present invention includes a gas cylinder (gas supply source) 8, high
energy particle generation parts 1-3 for exciting gas supplied from the
gas cylinder 8 so as to generate gas of temperature nonequilibrium
condition including high energy particles, and a gas injection part for
spraying external pathogenic organisms with the gas of temperature
nonequilibrium condition generated by the high energy particle generation
parts 1-3.

[0031]In the present embodiment, a single gas cylinder 8 is provided and a
single type of gas is supplied. However, a mixed gas of more than two
types of gases maybe supplied from different gas cylinders.

[0032]The high energy particle generation parts 1-3 include, according to
this embodiment, a microwave plasma source. The microwave plasma source
includes a plasma torch 3, a microwave power source 1, and a co-axial
cable 2 for supplying power from the microwave power source 1 to the
plasma torch 3. Although not shown, the plasma torch 3 includes a chamber
for receiving the gas supplied from the gas cylinder 8 and an
electromagnetic field generator for providing the chamber with an
electromagnetic field to excite gas in the chamber. In addition, the gas
injection part includes a plasma injection pipe 4 arranged in the plasma
torch 3.

[0033]Here in this embodiment, for safe operation of the apparatus, parts
other than the microwave power source 1 of the micro plasma source are
incorporated in a draft chamber 7.

[0034]According to the preferred embodiment, the plasma torch 3 includes a
cooling unit for cooling down the gas of temperature nonequilibrium
condition before the gas is introduced into the plasma injection pipe 4.
It is preferable that the plasma torch 3 includes a flow rate regulating
valve arranged at a gas supply port of the chamber. Furthermore, it is
preferable that at least one of the chamber of the plasma torch 3 or the
plasma injection pipe 4 is provided with means for mixing steam in the
gas of temperature nonequilibrium condition.

[0035]Thus, power is supplied from the microwave power source 1 to the
plasma torch 3 through the co-axial cable 2. Gas is supplied from the gas
cylinder 8 to the plasma torch 3. Then, plasma generated by the plasma
torch 3 is irradiated to a sample 5 fixed to the substrate 6 so as to
carry out sterilization.

[0036]In order to verity sterilization effect of the above-mentioned low
temperature dry disinfection device, experiments were conducted as
follows:

[0037]Frequency of microwave was 2.45 GHz, power was between 300 and 400W.
Argon, helium, and oxygen were used as gas and maximum flow rate of the
gas was 20SLM. A mixed gas of those gases could be used.

[0038]Irradiation distance was appropriately adjusted between 70 mm and
150 mm in such a manner that temperature on the substrate where the
sample 5 was set became 323K, 333K, 353K, and 383K, respectively. The
heated argon gas was supplied by supplying the argon gas through a
stainless pipe heated by an electric heater. Sterilization time was set
to 10 minutes, 20 minutes, 30 minutes, and 40 minutes, respectively.

[0039]For comparison with the low temperature dry disinfection device of
the present invention, sterilization by ultraviolet irradiation was
carried out. Using a mercury ultraviolet lamp (UV lamp), ultraviolet was
irradiated to a sample.

[0040]Temperature of the gas was measured by E-type thermocouple.
Bioindicator (3M, Attest 290) and a sample of No. 1291 were used. The
sample is a piece of paper coated with spores of Bacillus subtilis
existing in a natural environment.

[0041]Sterilization effect was checked by inserting the processed sample 5
into the bioindicator. When the sample is determined to be negative (-)
by the bioindicator, it is guaranteed that the spores of Bacillus
subtilis were sterilized by at least a log reduction number of 5
(10-5). On the other hand, when the sample is determined to be
positive (+), it means that the log reduction number is less than 5.

[0042]Condition of spores of Bacillus subtilis was photographed by use of
real surface microscope VE-7800 (product of KEYENCE). FIGS. 2-5 are
photographs of spores of Bacillus subtilis coated on the surface of the
samples obtained in this experiment. In FIG. 2, the spores of Bacillus
subtilis are not processed, in FIG. 3, the spores of Bacillus subtilis
are processed by the argon plasma irradiation (353K), in FIG. 4, the
spores of Bacillus subtilis are processed by the heated argon gas
irradiation (353K), and in FIG. 5, the spores of Bacillus subtilis are
processed by the UV irradiation. Each of the spores have a length of 1 to
2 μm and a shape of a cocoon. Distribution of the spores is not
uniform and the spores concentrate between fibers of paper. Difference in
condition among the spores for each process is not clearly found in the
photographs but the ratio of the concentration or the size of the spores
became smaller depending on the processes.

[0043]FIG. 6 is a graph showing difference in the sterilization ratio by
sterilization temperature and sterilization methods. In FIG. 6, the
sterilization ratio (%) is defined by (the number of sterilized
samples)/(the total number of the samples)* 100, where the sterilized
samples represent the samples determined to be negative (-) by the
bioindicator.

[0044]Following facts were found by the experiment: [0045](1) As the
sterilization temperature rises, the sterilization ratio rises. [0046](2)
Comparing between the argon plasma irradiation and the heated argon gas
irradiation, the argon plasma irradiation has higher sterilization ratio.

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Patent applications in class In situ generation of agent other than aldehyde or glycol

Patent applications in all subclasses In situ generation of agent other than aldehyde or glycol